Synthesis, structures and magnetic properties of the dimorphic Mn2CrSbO6 oxide

The perovskite polymorph of Mn2CrSbO6 compound has been synthesized at 8 GPa and 1473 K. It crystallizes in the monoclinic P2(1)/n space group with cell parameters a = 5.2180 (2) angstrom, b = 5.3710(2) angstrom, c = 7.5874(1) angstrom and alpha = 90.36(1)degrees. Magnetic susceptibility and magnetization measurements show the simultaneous antiferromagnetic ordering of Mn2+ and Cr3+ sublattices below T-N = 55 K with a small canting. Low temperature powder neutron diffraction reveals a commensurate magnetic structure with spins confined to the ac-plane and a propagation vector kappa = [1/2 0 1/2]. The thermal treatment of this compound induces an irreversible phase transition to the ilmenite polymorph, which has been isolated at 973 K and crystallizes in R (3) over bar space group with cell parameters a = 5.2084 (4) angstrom and c = 14.4000 (11) angstrom. Magnetic susceptibility, magnetization and powder neutron diffraction data confirm the antiferromagnetic helical ordering of spins in an incommensurate magnetic structure with kappa = [00 0.46] below 60 K, and the temperature dependence of the propagation vector up to kappa = [00 0.54] at about 10 K.